You have been given some good advice already.

Do try to find a CL club or at least some experienced flyers. Many clubs have trainers available and you outgrow trainers very quickly.

The original Flite Streak called for a baffle .19 to .35. Your OS .25 has more power than the old .35's. Forget anything larger. Some have flown the FS with an OS FP-.15. A .20-.25 seems to be the preferred size. The ARF Flite Streak would be good as a second plane...after a trainer.

Do pay attention to balancing it about 1" to 1.5" behind the leading edge of the wing. Several flyers have reported losing the plane because it was balanced too far aft.

You have obstacles to overcome such as getting dizzy when turning with the model, and getting used to the controls.

I am assuming that your .25 is throttled. You can just wire the throttle open. No need for a dedicated CL engine at this stage.

A .049 model is harder to fly but is much less likely to break when crashed (fly over grass...very important).

Do you have any 1/2A engines? A Sig Skyray and a Cox tank-mounted engine are hard to beat for a beginner. It explains easy changeable options for minimum control setup for beginning (stable as trainer) and later increasing control movement as you gain experience.

Whichever model, use a narrow control spacing on the handle. This will also provide minimal control at first, which you can easily change later on.

Welcome to CL flying. Keep us posted...and ask lots of questions.

George